Abstract
Purpose :
Structural changes of the limbal stem cell niche are unknown in many ocular pathologies. Although studies have characterized the shape of the focal stromal projections of the palisades of Vogt, there is a dearth of studies examining the macroscopic structure of the limbal crypts. Consequently, a method for measuring the volume of the limbal crypts using visible-light optical coherence tomography (vis-OCT) imaging was developed.
Methods :
One ex vivo human eye, positioned in a region where the palisades were most visible, was imaged with vis-OCT. A raster scan pattern with a field of view of 1 mm by 1 mm was used to acquire two images of the eye at different times and slightly different locations. For volume calculation, the first step was to identify the surface of the limbus. A combination of thresholding, outlier removal, and 3D parabola fitting was used to determine this surface. Next, the boundary of the stromal projections was identified. The inverse gradient was calculated and a fast marching scheme using the inverse gradient found the boundary of the stromal projections. An initial mask found from a threshold that under segmented the limbal crypts was used as a seed for the marching algorithm. An alternate method based on manual thresholding to find the stromal projection surface was implemented for comparison. The volume of the limbal crypts is the volume between the limbal surface and stromal projections.
Results :
Repeated measurements of limbal crypt volume at slightly different locations yielded volume measurements of 3.5*107 cubic microns and 2.7*107 cubic microns. Volume changed by less than 2% as parameters differed when the fast marching scheme was used to determine the stromal projection boundary. However, volume changed by up to 27% when different manual thresholds were used.
Conclusions :
We developed a method that is robust to changes in parameters for measuring the volume of limbal crypts. Such measurement has the potential to serve as a parameter for monitoring the health of the stem cell niche. However, additional investigation is needed to examine the consistency and capability in identifying pathological alterations.
This is a 2021 ARVO Annual Meeting abstract.